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Stefan died in hospital on Saturday and two other festival goers from the Adelaide event, a man, 20, and a 21-year-old woman, remain in a critical but stable condition.

SA Police are investigating whether the same pills - pink and with a dollar sign imprint - were involved in all three cases.

There was another death at Stereosonic's Sydney event when pharmacist Sylvia Choi, 25, was struck down, again by a suspected drug overdose.

A young Victorian man also remains in a serious but stable condition in intensive care, again from a suspected drug overdose, after Stereosonic held its Melbourne event on Saturday.

The Stereosonic Music Festival, which holds events across the major capitals from Nov 28 to Dec 6, is holding its final Brisbane-based event on Sunday.

The festival deaths have sparked calls for drug testing services to be allowed at Australian events so users know what they are taking.

The mother of a Melbourne man who died after taking drugs at a Victorian music festival in 2012 has collected 33,000 signatures so far in her Change.org campaign for drug testing services at festivals.

"Until we wise up and accept the reality that drug testing services are the only way forward, kids like my son and the most recent man in Adelaide - another mum's poor son - will continue to die," Andriana Buccianti said.

SA Police Superintendent John De Candia said such services were a matter for governments.

"If you want to be 100 per cent certain in relation to illicit drugs, if you want to be safe, the message is clear - don't take them," he said.

South Australian independent senator Nick Xenophon wanted to know what duty of care the organisers felt they had to the young people at the festival.

"I have heard from people whose children went to this event ... that there were people snorting drugs off people's foreheads ... that there were so many people that were completely out of it," he said.

Prime Minister Malcolm Turnbull sent his condolences to the Adelaide man's family, after he announced $300 million in new funding for treatment, prevention and education to tackle the ice scourge.

SA Opposition Leader Steven Marshall said pill testing would send a dangerous message to young people that drug taking was safe when it wasn't under any circumstances.